Known is the machine for flash-butt (Author's Certificate, USSR, No. 201561 of 09.1967, B18, cl. 21h,29), comprising two tong-type clamps which are set into motion by clamping hydraulic cylinders. The tong-type clamps are mounted on a common axle. The right clamp can only rotate around its own axis, while the left one, except this, can move along it. The axial displacement of the left clamp is performed by means of two cylinders of upsetting, which operate synchronously from a common hydraulic line. Two welding transformers, connected in parallel, are built into the right clamp levers. The clamping is realized in a rail web using current-carrying copper jaws, manufactured to fit a rail web profile. The welding current to the clamping jaws of the right clamp is supplied' by rigid jumpers from the welding transformer. The current to the clamping jaws of the left clamp is supplied through rods of the upsetting cylinders, electric contacts-yokes and flexible jumpers, arranged inside the left clamp body, thus avoiding the damage of flexible jumpers by molten metal drops in the process of rails flashing. The right clamp is isolated from the left one in rods by using isolating bushings. The driving of the left clamp with respect to the right one in the process of flashing and upsetting is realized automatically by a special speed controller according to a preset program through a hydraulic servo slide valve, built-in into a central axle.
The main drawback of the machine is an insufficient length of flexible current-carrying jumper which does not allow making operation for pulling the long rail sections at a required force.
Machine for the flash-butt welding of rails (Patent of Ukraine No.56986 of, 06.2003, BNo.6, 2003, MBK7 B23KI1104), taken as a prototype, comprising two tong-type clamping devices made in the form of double-arm levers mounted on a common axle and isolated one from another, hydraulic cylinders of clamping and displacement of parts being welded, two welding transformers, built into the arm of the lever of one of two tong-type clamping devices and current-carrying elements which include rods of displacement and upsetting, electric contacts-yokes and flexible jumpers.
The above-described welding machines, including also a prototype, have flexible current-carrying jumpers of a limited length, which are fixed on an electric contacts-yoke, and it, in turn, is permanently connected to the rod of displacement and upsetting of the machine during its assembly. This limited length of the jumpers is not enough for the welding of long sections under field conditions, when it is necessary to provide the pulling of the rail section to be welded on at a required force before the welding process proper by increasing the travel of rods of displacement and upsetting for a distance which exceeds greatly that of the parts displacement necessary directly for the welding process.
The increase in travel of rods of the displacement and upsetting requires the appropriate elongation of flexible current-carrying jumpers. That leads to a significant increase in the resistance of the electric circuit of the welding machine, instability of the welding process and, as a consequence, to the appearance of non-quality welded rail joints. So, to arrange the elongated flexible current-carrying jumpers, it is necessary to increase also the sizes of tong-type clamps, thus increasing the weight and dimensions of the machine.